hyperarousal . Physiological drivers can arise from body systems , such as the respiratory , cardiovascular , endocrine , gastrointestinal , nervous , muscular , and reproductive systems , where homeostasis has been negatively affected by stress . Disruption in any of these systems can lead to functional symptoms that can produce conditions that in turn play a role in perpetuating the stress response .
Disruption of body systems by stress can be assessed through various questionnaires and through measures such as heart rate variability . Given the close relationship between breathing dysregulation and stress overload , breathing questionnaires such as the Nijmegen Questionnaire can be helpful for identifying stress symptoms tied to dysfunctional breathing .( 15 )
Improve the function of the stress response system
Lifestyle and supportive measures such as sleep hygiene , a healthy diet , improved gut microbiome , social support , and work-life balance are all fundamental to improving the function of the stress response system . Psychological therapies and mental training , using tools such as mindfulness and cognitive behavioral therapy ( CBT ), can be very useful in improving self-regulation of the stress response system . These tools can be helpful in conjunction with body-based therapies to improve nervous system arousal and self-regulation . Some examples are :
• Vagal nerve stimulation ( 16 )
• Massage and muscle relaxation techniques ( 17 )
• Breathing retraining ( 18 )
• Mind body therapies such as Eye Movement Desensitization and Reprocessing ( EMDR ), yoga and mindfulness ( 19 , 20 ).
Increase stress resilience
Good stress , that increases the body ’ s adaptive capacity and stress resilience , can be applied through means such as exercise , fasting , cold exposure , sauna and fasting , as well as breathing therapies such as deliberate hyperventilation and Intermittent Hypoxic Hyperoxic Training ( IHHT ). Hyperbaric Oxygen Therapy ( HBOT ) is also a type of stress , providing increased oxidative stress by means of increased oxygen delivered under pressure .
The good news is that one does not need to reduce all sources of stress , or work with every available approach , to engage in an upward spiral towards the recovery of a disordered stress response system . Working with physiology can improve psychological function , and improving psychological function can enhance physiology . Additionally , optimising the function of a single body system can have positive flow-on effects for other systems , ultimately benefiting the stress response system .
Breathing and stress
As outlined , the respiratory system plays a central role in the body ' s stress response and can be easily disrupted by various forms of stress . However , this relationship between stress and breathing is bidirectional : stress affects breathing patterns , and disordered breathing can maintain the stress response .
Breathing needs to constantly change to maintain physiological homeostasis . While it is primarily regulated for metabolic activity , it also responds to changes in emotion , mental patterns , and activation levels in the limbic system .( 21 ) Mental , emotional , and physiological stressors that activate our threat system can create physiological hyperarousal , stimulating the respiratory system . Acute or short-term stress typically causes normal respiratory changes as a response to the need for immediate action . However , when hyperarousal is chronic or occurs too frequently without adequate recovery time , it can disrupt breathing control systems , including the HPA and SAM systems , leading to disordered or dysfunctional breathing such as hyperventilation , breathing pattern disorders , and unexplained breathing discomfort .
Chronic disordered breathing can contribute to allostatic load , creating a feedback loop where disordered breathing maintains hyperarousal in the stress response system . Hyperventilation , breathing pattern disorders , and unexplained breathing discomfort are common in patients with anxiety and panic disorder .( 22 ) These breathing disorders can perpetuate dysregulation in the autonomic nervous system and brain chemistry , maintaining hyperarousal in the stress response system .( 8 , 23 , 24 )
The interaction between hyperventilation in anxiety and panic disorder has been studied for many decades . Two key theories explain the effect of hyperventilation on these systems : Ley ’ s hyperventilation theory suggests that it causes panic symptoms , while Klein ’ s suffocation false alarm theory views hyperventilation as a compensatory response to an oversensitivity of the brain chemoreceptors to the rise in normal levels of CO2 .( 25 , 26 )
Recent research implicates the amgydala in the chronic breathing dysregulation and hyperventilation found in anxiety disorders .( 8 ) Feinstein ( 2022 ) proposes that recurring episodes of amygdala-driven apnoea lead to CO2 hypersensitivity and chronic anxiety . This hypersensitivity , driven by the amygdala and other acid-sensing brain regions , causes individuals to experience anxiety and suffocation fear with small and physiological increases in CO2 . This contributes to vicious circles of chronic heightened anxiety , low CO2 , and instability of breathing control .
Breathing training that increases tolerance to CO2 can effectively normalise CO2 responses in the body , leading to stable and significant reductions in anxiety and panic attacks . A series of studies by Meuret and colleagues over a decade showed that breathing training aimed at building CO2 tolerance using controlled breathing was highly effective in reducing panic symptoms , anticipatory anxiety and fear avoidance behaviour .( 27-31 )
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